| growmodel.sim {FSA} | R Documentation |
Plots hypothetical size-at-age for one of three possible parameterizations of the von Bertalanffy, two possible parameterizations of the Gompertz, and the Schnute growth models. Slider bars are used to alter the parameters of each model
growmodel.sim(model="vb",x=NULL,y=NULL,max.len=500)
model |
A character string identifying which growth model to use. See details. |
x |
An optional vector containing observed ages. See details. |
y |
An optional vector containing observed lengths. See details. |
max.len |
A numeric indicating the maximum length to use in the simulations. |
This function is best used for exploring the “shape” of the model for various choices of a single parameter while holding the other parameter constant. Both parameters can be changed in the simulations but the results are more difficult to interpret. For model exploration the x and y arguments should be left set at NULL.
This function can be used to visually “fit” a growth model to a set of observed ages and lengths in order to determine reasonable starting values for the non-linear least-squares fit of a growth model. Observed data are plotted by included the vector of observed ages in the x argument and the vector of observed lengths in the y argument.
The model argument is used to choose the model to use and must be one of the following (the models are described in detail in the FSA text):
"vb" | The traditionally parameterized von Bertalanffy model. |
"vb2" | The “second” Schnute-like paramaterization of the von Bertalanffy model. |
"vbgq" | The Galucci & Quinn (1979) parameterization of the von Bertalanffy model. |
"gomp1" | The “first” parameterization of the Gompertz model. |
"gomp2" | The “second” parameterization of the Gompertz model. |
"gomp3" | The “third” parameterization of the Gompertz model. |
"schnute" | The Schnute(1981) four-parameter general growth model. |
Once the function is submitted a dialog box will appear in which the user can change the minimum and maximum age over which the growth model is evaluated and change the parameters specific to the growth model. The meanings of each parameter are discussed in the FSA text.
The slider object has a tendency to “disappear” when focus is put on the plot. The slider object can be brought back to the foreground by finding the object listed on the Windows toolbar. The slider object should be “exit”ed when finished exploring a model.
None. However a dynamic graphic connected to slider bar controls is produced.
Derek H. Ogle, dogle@northland.edu
Galucci, V.F. and T.J. Quinn II. 1979. Reparameterizing, fitting, and testing a simple growth model. Transactions of the American Fisheries Society, 108:14-25.
Schnute, J. 1981. A versatile growth model with statistically stable parameters. Canadian Journal of Fisheries & Aquatic Sciences, 38:1128-1140.
Schnute, J. and D. Fournier. 1980. A new approach to length-frequency analysis: Growth structure. Canadian Journal of Fisheries and Aquatic Sciences, 37:1337-1351.
## Not run: ## These examples cannot be run by examples() but should work in an interactive R session ## Not run: growmodel.sim() # Using the defaults ## Not run: growmodel.sim(model="schnute") # Schnute model using the defaults ## Not run: data(Croaker2) # Atlantic Croaker data set ## Not run: crm <- Croaker2[Croaker2$Sex=="M",] # Just the males ## Not run: attach(crm) ## Not run: growmodel.sim(model="gomp2",x=Age,y=TL,max.len=500)